Conclusion

Evaporation-driven WEG devices have gained significant attention since water is highly available and can easily evaporate. Several studies utilizing inorganic nanomaterials tend to overshadow the utilization of easily accessible organic materials. This study presents an innovative electricity generation method that employs the nutshell (NS) structures by leveraging the process of streaming potential and water evaporations. This revolutionary bio-based technology is presented for the first time and utilizes inherent hierarchical porous structures of NSs for efficient ion transfer, enabling the WEG device to function sustainably with minimum water intake. Amongst the four NSs investigated, walnut shell (WS) exhibits superior performance due to its uniform pore distributions, surface charge, and efficient water uptake and release capabilities. Other NSs are also a promising source of WEG that need further attention. A consistent electric output over 550 mV for a duration of one week, demonstrates the long-term stability of the WS-WEG. Moreover, this WS-WEG functional device’s incredible power density (5.96 µW·cm−2) indicates its enormous potential for practical use. A notable enhancement of the voltage and current density is observed by utilizing nanoengineering techniques that enhance the number of nanopores. Furthermore, placing the nano-engineered WS-H+ into an alkaline reservoir shows a significant rise in voltage to 1.21 V and a maximum current density of 347.2 μA/cm2. This enhancement could be attributed to the combined synergetic impacts of physical and chemical mechanisms. By connecting two units in series and two units in parallel, this WS-H+ can power a calculator without the aid of any rectifiers, indicating the potentiality of this WEG device as a sustainable power source for compact electronics. In summary, this work not only develops the comprehension of nutshell-based WEG but also offers a feasible, low-cost, sustainable energy source utilizing agro-industrial waste to power electronic devices.